The invention relates to a multi-leaf collimator, preferably for controlling a shape of a high-energy radiation beam emanating from a radiation source and propagating in a direction of propagation. In a preferred aspect, the invention relates to a multi-leaf collimator with leaf drives, with two sets of displaceable leaves arranged side by side facing each other in order to impress a high-energy beam with the shape of an irregularly formed treatment object by enabling each of the leaves to assume a position oriented along the shape of the treatment object by means of a leaf drive, with the leaf drives being designed in such a way that the each of the leaves is each equipped with a gear rod-like drive engagement in the direction of the displacement. As known in the art, the term “gear-rod-like drive engagement” can also be referenced by the English term “rack” or “rack gear”.
The treatment devices used today in oncological radiation therapy are equipped with collimators that delimit high-energy beams, in most cases high energy radiation of a linear accelerator, in such a way that the beams have exactly the same shape as the treatment object. Since such radiation, e.g. of a tumor, occurs from various directions, it is possible to achieve a great irradiation intensity of the tumor and, at the same time, to stress the surrounding tissue only to a limited extent.
The leaves of the multi-leaf collimator may also be called “shutter blades” or “lamellae”. The multi-leaf collimators may also be called contour collimators since due to the positioning of the leaves, contours of treatment objects, for example tumors, can be recreated for each beam application, each of which occurs from a certain solid angle. This is important in order to protect the adjacent healthy tissue to the greatest extent possible. In the case of critical tissue such as nerves, this is particularly necessary in order to preserve their functional capability.
A multi-leaf collimator of the kind mentioned at the beginning has been known, for example, from EP 0 387 921 A2. Since in the case of such multi-leaf collimators, each leaf must be moved into a certain position, in most cases a drive must be assigned to each leaf. In the case of the aforementioned publication, not every leaf is assigned a motor, which is why the leaves are arranged in series by means of drive couplings and locking devices. However, it has also been known to assign an electric motor to each leaf that positions the leaves via a pinion and a gear rod-like drive engagement.
However, the more precisely the shape of the treatment object, e.g. of a tumor, is to be recreated, the more and thinner leaves will be required. This means that a large number of electric motors and drive transmissions to the leaves must be housed in an extremely small space. In addition, these drives must be arranged in one area in such a way that they will be located within an irradiation head containing the radiations source and the collimator in an area in which structural space is available.
Since for an irradiation, the irradiation head usually must be moved into various solid angles relative to the target volume, e.g. the tumor, it is desirable to design such a collimator as compact and lightweight as possible. In this way, a gantry or a robot arm that move the irradiation head into these solid angle positions can also be constructed with less weight, thereby making them faster movable into various positions and more mobile.